Wattflyer RC Network: RC Universe :: RCU Magazine :: RCU Forums :: RCU Classifieds :: RCU User Reviews :: RCU YouTube
Home Who's Online Calendar Today's Posts RealTime Post Spy Mark Forums Read
Go Back   WattFlyer RC Electric Flight Forums - Discuss radio control eflight > Electric R/C Airplanes > Foamies
Register Members List Wattflyer Extras Articles Search Today's Posts Mark Forums Read Social Groups

Foamies Talk about building, power setups and anything having to do with e-powered foamy planes!

Thank you for your support (hide ads)
Reply
 
Thread Tools Display Modes
Old 09-20-2012, 02:21 PM   #1
npowell28
Member
 
Join Date: Nov 2010
Posts: 100
Thanked 0 Times in 0 Posts
iTrader: (0)
Friends: (0)
Default My latest build - worried about the motors

Attached is a photo of my latest build 54 inch cargo type plane very loosely based on a c130. (it's not finished yet). Total weight when finished will be about 50oz, wing area of 430 sq inches giving a wing loading of 16-17 oz per sq foot.

I'm planning to use 2 x Keda TR 2837/18 motors(see flybrushless for details)

http://www.flybrushless.com/motor/view/494

I might have cocked up a bit. I was planning to use 10 inch props but that doesn't give me a great deal of ground clearance. I fly off a cricket pitch so i can see there being a few broken props. I'm thinking of dropping down to an 8 or 9 inch prop. Flybrushless results show that using a 3s battery the thrust with a 9x5 prop will give over 20oz's of thrust. Obviously that will give me about 40 oz's of thrust.

Just spotted my deliberate mistake. I read somewhere that thrust:model weight ratio should be 1:3 not 3:1 as i originally posted.

Cheers everyone


Attached Thumbnails
Click image for larger version

Name:	c130 replica.jpg
Views:	194
Size:	253.1 KB
ID:	162717  
npowell28 is offline  
  Reply With Quote
Old 09-20-2012, 07:09 PM   #2
rcers
Community Moderator
 
rcers's Avatar
 
Join Date: Jul 2005
Location: Trophy Club TX
Posts: 6,202
View rcers's Gallery57
Thanked 502 Times in 492 Posts
Awards Showcase

WAA-08 Pilot 
iTrader: (4)
Friends: (9)
Default

Originally Posted by npowell28 View Post
sI read somewhere that thrust to model weight ratio should be 3:1. Is this right??

Cheers everyone
Heavens no. That is super stunning power - well past what is needed. Forget about thrust. There are much better ways to assess motors - most use watts per pound for a better idea.

Mike
rcers is offline  
  Reply With Quote
Old 09-20-2012, 07:48 PM   #3
pmullen503
Member
 
Join Date: Mar 2011
Posts: 850
Thanked 71 Times in 70 Posts
Awards Showcase

Scratchbuilders Award 
iTrader: (0)
Friends: (3)
Default

You'll have plenty of power for a cargo type plane. Looks like you can "prop up" to a 9x6 or 9x7 if you feel the need without stressing your motors.

Your wing loading is very reasonable, you'll probably find you can fly around nicely at 1/2 to 3/4 throttle.

It's never too late to have a happy childhood.
pmullen503 is offline  
  Reply With Quote
Old 09-20-2012, 08:03 PM   #4
mclarkson
Super Contributor
 
mclarkson's Avatar
 
Join Date: May 2010
Location: Wichita, KS
Posts: 2,951
View mclarkson's Gallery4
Thanked 179 Times in 177 Posts
Awards Showcase

Scratchbuilders Award  Outstanding Contributor Award 
iTrader: (0)
Friends: (7)
Default

Planes fly just fine with less that 1:1 thrust-to-weight. I believe a 747 has a thrust-to-weight ratio in the neighborhood of 1:3 or 1:4, for example.

3:1, as was stated before, is crazy, crazy power. That's for 3D planes and speed record attempts.

mclarkson is online now  
  Reply With Quote
Old 09-20-2012, 08:29 PM   #5
npowell28
Member
 
Join Date: Nov 2010
Posts: 100
Thanked 0 Times in 0 Posts
iTrader: (0)
Friends: (0)
Default

Originally Posted by rcers View Post
Heavens no. That is super stunning power - well past what is needed. Forget about thrust. There are much better ways to assess motors - most use watts per pound for a better idea.

Mike
Thanks all. AUW will be about 52 oz's.
npowell28 is offline  
  Reply With Quote
Old 09-21-2012, 12:26 AM   #6
npowell28
Member
 
Join Date: Nov 2010
Posts: 100
Thanked 0 Times in 0 Posts
iTrader: (0)
Friends: (0)
Default

Originally Posted by npowell28 View Post
Attached is a photo of my latest build 54 inch cargo type plane very loosely based on a c130. (it's not finished yet). Total weight when finished will be about 50oz, wing area of 430 sq inches giving a wing loading of 16-17 oz per sq foot.

I'm planning to use 2 x Keda TR 2837/18 motors(see flybrushless for details)

http://www.flybrushless.com/motor/view/494

I might have cocked up a bit. I was planning to use 10 inch props but that doesn't give me a great deal of ground clearance. I fly off a cricket pitch so i can see there being a few broken props. I'm thinking of dropping down to an 8 or 9 inch prop. Flybrushless results show that using a 3s battery the thrust with a 9x5 prop will give over 20oz's of thrust. Obviously that will give me about 40 oz's of thrust.

Just spotted my deliberate mistake. I read somewhere that thrust:model weight ratio should be 1:3 not 3:1 as i originally posted.

Cheers everyone
Sorry spotted my deliberate mistake so edited my earlier comment for continuity.
npowell28 is offline  
  Reply With Quote
Old 10-07-2012, 11:46 AM   #7
npowell28
Member
 
Join Date: Nov 2010
Posts: 100
Thanked 0 Times in 0 Posts
iTrader: (0)
Friends: (0)
Default

Update, I haven't flown it yet but i've put the watt meter on it. 135 watts per motor on 10 x 6 props and 150watts on 3 bladed 10 x 7 props. This is on freshly charged batteries so it should take off ok. According to my very unscientific test, digital scales against the wall, its giving nearly 3lbs of thrust. It certainly got all the dust out from behind the radiators.

I'll update as soon as i've tested it.
npowell28 is offline  
  Reply With Quote
Old 10-07-2012, 04:24 PM   #8
dahawk
Super Contributor
 
dahawk's Avatar
 
Join Date: Jul 2011
Location: Keller, TX
Posts: 3,387
View dahawk's Gallery6
Thanked 205 Times in 201 Posts
Club: 114th RC Aero Squadron
iTrader: (0)
Friends: (19)
Default

Very nice plane. With that kind of power, you have a STOL
like the full scale C-130

Let us know how she flies !

- hawk
dahawk is offline  
  Reply With Quote
Old 10-07-2012, 06:44 PM   #9
npowell28
Member
 
Join Date: Nov 2010
Posts: 100
Thanked 0 Times in 0 Posts
iTrader: (0)
Friends: (0)
Default

Originally Posted by dahawk View Post
Very nice plane. With that kind of power, you have a STOL
like the full scale C-130

Let us know how she flies !

- hawk
Will do. Haven't got much work left to do now. Trying to figure out the best way to paint it. It's either that or i'm just putting off that maiden. Suppose you've gotta give it a go at some point. LOL
npowell28 is offline  
  Reply With Quote
Old 10-23-2012, 01:04 PM   #10
npowell28
Member
 
Join Date: Nov 2010
Posts: 100
Thanked 0 Times in 0 Posts
iTrader: (0)
Friends: (0)
Default

Tokk it out for its test flight today. It flew but just seemed to lack power. I made sure that the COG was fine. If anything it was more weighted towards the front. Just seemed to fly a bit tail down. It was just a tiny bit but seem to lack authority. The motors only give 110w each and the plane weighs 3lb on the dot so i'm guessing that they just need a little bit more power. I've tried a new motor that gives 150w on an 8 x 4 prop so i'll give them a go i think.

Apart from that looks cool in the air.
npowell28 is offline  
  Reply With Quote
Old 10-23-2012, 01:57 PM   #11
npowell28
Member
 
Join Date: Nov 2010
Posts: 100
Thanked 0 Times in 0 Posts
iTrader: (0)
Friends: (0)
Default

Just an after thought, i expect that the this could be the nose pitching up due to not enough/no downward thrust on the motors. I'll add some and give it another try.,
npowell28 is offline  
  Reply With Quote
Old 01-18-2013, 11:55 AM   #12
subzJC
flyer
 
Join Date: Oct 2012
Location: knoxville
Posts: 37
Thanked 5 Times in 3 Posts
iTrader: (0)
Friends: (0)
Default

How did your motor swap work out for you?
I hope you still have your airplane, atleast in one or two pieces.
Please share your story.
Thanks!
subzJC is offline  
  Reply With Quote
Old 01-19-2013, 05:08 PM   #13
npowell28
Member
 
Join Date: Nov 2010
Posts: 100
Thanked 0 Times in 0 Posts
iTrader: (0)
Friends: (0)
Default

Originally Posted by subzJC View Post
How did your motor swap work out for you?
I hope you still have your airplane, atleast in one or two pieces.
Please share your story.
Thanks!
Hi thanks for the interest. After my initial test flight, my make shift runway(cricket wicket) became really wet and bumpy. This planes belly is really low to the floor and needs a good surface to fly off. So unfortunately it's in the hanger, well on top of my wardrobe, until the better weather comes back.

Having thought about it though, it should really have enough power on the motors it has. I am going to lessen the angle of attack somewhat by raising the trailing edge by a couple of mm and go from there. If that doesn't have the result i'm looking for then i'll change the motors. I do think though that having more power will just make the balooning worse.

I'll have to wait until spring arrives unfortunately before i find out.

It did give me time to paint it though. I'll post some pictures next time i get it off the wardrobe.
npowell28 is offline  
  Reply With Quote
Old 01-23-2013, 12:27 PM   #14
subzJC
flyer
 
Join Date: Oct 2012
Location: knoxville
Posts: 37
Thanked 5 Times in 3 Posts
iTrader: (0)
Friends: (0)
Default

npowell,

thanks for the reply!
Most times it is best to take extra time to think about a problem.
Any chance of doing turf maintenance on the cricket wicket?
I would really like to see the paint job you put on the airplane.

Have a good one!
subzJC is offline  
  Reply With Quote
Old 01-24-2013, 08:17 AM   #15
npowell28
Member
 
Join Date: Nov 2010
Posts: 100
Thanked 0 Times in 0 Posts
iTrader: (0)
Friends: (0)
Default

Originally Posted by subzJC View Post
npowell,

thanks for the reply!
Most times it is best to take extra time to think about a problem.
Any chance of doing turf maintenance on the cricket wicket?
I would really like to see the paint job you put on the airplane.

Have a good one!
No i'll have to wait for the better weather. Don't want to mess up the work that the groundsmen do.
npowell28 is offline  
  Reply With Quote
Old 01-24-2013, 08:01 PM   #16
npowell28
Member
 
Join Date: Nov 2010
Posts: 100
Thanked 0 Times in 0 Posts
iTrader: (0)
Friends: (0)
Default

Ok this is the paint scheme so far. The blue painted window will be replaced shortly with a cockpit and proper windows. Motors will also get covers when i get the chance.


Attached Thumbnails
Click image for larger version

Name:	20130124_134547.jpg
Views:	54
Size:	354.0 KB
ID:	165849  
npowell28 is offline  
  Reply With Quote
Reply

  WattFlyer RC Electric Flight Forums - Discuss radio control eflight > Electric R/C Airplanes > Foamies

« Previous Thread | Next Thread »

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
$100 Scratch Build Contest "Best Looking" poll here hillbillynamedpossum Scratch and Kit Built Aircraft 107 08-26-2013 11:23 PM
For Sale Aluminum Motor Mounts for Multiplex, Parkzone, and Flyzone Super Cub Planes terrynshed Motors and Speed Controllers for sale & WTB 4 09-24-2012 05:33 PM
Modified GWS Slow Stick, My latest build... svo ParkFlyers 11 03-25-2012 12:21 AM
GWS ME-109, latest build tarheal63 Warbird Electrics 8 03-03-2012 04:10 PM
For Sale Aluminum motor mount for Parkzone T28 / Corsair 3530/3536/3542 series motors terrynshed Motors and Speed Controllers for sale & WTB 2 12-16-2010 05:00 PM


All times are GMT +1. The time now is 09:38 PM.


Powered by: vBulletin
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright 2005 WattfFlyer.com
RCU Eflight HQ

Charities we support Select: Yorkie Rescue  ::  Crohn's & Colitis Foundation



Page generated in 0.34437 seconds with 53 queries